Course of illness in a sample of patients diagnosed with a schizotypal disorder and treated in a specialized early intervention setting. Findings from the 3.5year follow-up of the OPUS II study.

Background: Previous studies report that 20% to 30% of those initially diagnosed with schizotypal disorder go on to develop a psychotic disorder (predominantly schizophrenia). Schizotypal disorder share some traits of those used to identify patients at ultra-high risk for psychosis.
Method: As part of a randomized clinical trial testing the effect of prolonged specialized early intervention, we recruited 83 participants diagnosed with a schizotypal disorder. Participants were recruited 18 months into their two-year treatment program, and follow-up interviews were conducted three and a half year later. They were randomized to either discontinuation after the standard two year treatment or continuation of the specialized treatment for totally five year. The study investigated whether prolonged treatment could affect the rate of transition to psychosis and other clinical outcomes, and what would predict transition to psychosis.
Results: Of those 59 who attended the follow-up interview 19 (32%) developed a psychotic disorder at follow-up. There were no differences between the two treatment groups on transition rates or clinical outcomes. We found that lower level of functioning at baseline predicted transition to psychosis.
Discussion: Comparable to previous ultra-high risk studies, we found that level of functioning was the strongest predictor of transition to psychosis. Prior studies have found effect of specialized early intervention on transition rates, but we were not able to reproduce this finding. This may be attributable to the intervention in our study occurring at a later stage in the illness than prior studies.
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